SMC (Sheet Molding Compound) and stampable sheets are known as molding materials which are excellent in mechanical properties of molded articles and suitable for forming complex shapes such as three-dimensional shapes. The SMC is a sheet-shaped fiber-reinforced resin material obtained, for example, by impregnating a thermosetting resin such as an unsaturated polyester resin between fiber bundles obtained by cutting reinforced fibers such as glass fibers and carbon fibers. In addition the stampable sheet is a sheet-shaped fiber-reinforced resin material obtained, for example, by impregnating a thermoplastic resin into the above-described cut fiber bundle.
The SMC is an intermediate material for obtaining molded articles. When molding the SMC compressing (pressing) the SMC with heating using a mold is used. At this time, the fiber bundle and the thermosetting resin are filled into the cavity of the mold while flowing together, and after that, the thermosetting resin is cured. Therefore, by using the SMC it is possible to obtain molded articles of various shapes such as those having partially different thicknesses, those having ribs bosses, or the like. In addition, molded articles of the stampable sheet can be obtained by heating up to the melting point or more of a thermoplastic resin by an infrared heater or the like and cooling and pressing with a mold at a predetermined temperature.
In manufacturing the above-described SMC (fiber-reinforced resin material), a paste containing a thermosetting resin is applied on a sheet (carrier) to be conveyed, after that an elongated fiber bundle is cut into predetermined-length fiber bundles, and the predetermined-length fiber bundles are scattered on the paste (refer to, for example, Patent Literature 1).
However, according to the manufacturing method in the related art, the directions of the fiber bundles scattered on the paste tend to be aligned in a certain direction, and thus, directionality may occur in the strength of the manufactured SMC. Specifically, the fiber bundles that are cut by the cutting machine and dropped tend to collapse in the conveying direction of the sheet when landing on the conveyed sheet and tend to be aligned in the direction along the conveying direction of the sheet. In addition, as the length of the cut fiber bundles becomes longer or the conveying speed of the sheet becomes faster, this tendency appears more remarkably.
Therefore, in the SMC obtained by the manufacturing method in the related art, the strength thereof is increased in the conveying direction (longitudinal direction) of the sheet, and the directionality easily occurs such that the strength thereof becomes weaker in the direction (width direction) perpendicular to the conveying direction of the sheet. Therefore, in manufacturing the SMC, it is necessary to allow the directions of the fiber bundles scattered on the paste to be irregular (random) so that no directionality occurs in the strength of the SMC as described above. For example, although the directionality of this strength can be reduced by decreasing the conveying speed of the sheet, in this case, the productivity of the SMC is deteriorated. The same description is also applied to the case of the stampable sheet.
As a measure for allowing the orientations of the fiber bundles to be irregular, in the following Patent Literature 1, a method of uniformly dispersing the fiber bundles without directionality by tapping fiber bundles that are cut by a cutting machine and dropped with a rotating drum has been disclosed. However, when this method is used, fluff (fiber scrap) is generated from the fiber bundles tapped with the rotating drum. In particular, since the fiber bundles are loosened the more the rotation speed of the rotating drum is increased, the more fluff occurs. In addition, a drive source for rotationally driving the rotating drum is required.